And from the authors' perspectives, the digital book is easily stolen and given away for free at pirate sites. Getting your work removed from all such sites is like playing Wack-a-Mole. My books were never big sellers, but they're widely available without me seeing a penny.
When you buy a digital book, you presently get the lowest level of software to read it for free; you can download a program or app that lets you read on your PC, tablet/notebook, or phone. You don't have to buy a Kindle. If you keep another device functioning with such software, even if it becomes obsolete it will still be able to read those books.
The hard facts of business is that no business is too large to fail. Those lifetime warranties are for the lifetime of the company, nothing more.